BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 4,563	$ 4,976
Less: Premium deficiency reserve	0	(176)
Less: Reinsurance recoverables	(76)	(85)
Balance	4,487	4,715
Incurred related to:
Current year	22,576	23,211
Prior years	(345)	(435)
Total incurred	22,231	22,776
Paid related to:
Current year	(18,332)	(18,720)
Prior years	(3,626)	(3,925)
Total paid	(21,958)	(22,645)
Premium deficiency reserve	0	(337)
Reinsurance recoverable	(78)	(75)
Ending balance	4,838	5,258
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	3,507	3,600
Less: Reinsurance recoverables	(76)	(85)
Balance	3,431	3,515
Incurred related to:
Current year	20,010	19,259
Prior years	(287)	(299)
Total incurred	19,723	18,960
Paid related to:
Current year	(16,385)	(15,766)
Prior years	(2,707)	(2,946)
Total paid	(19,092)	(18,712)
Reinsurance recoverable	(78)	(75)
Ending balance	4,140	3,838
Total IBNR	2,700
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	578	616
Incurred related to:
Current year	2,629	2,556
Prior years	(31)	(38)
Total incurred	2,598	2,518
Paid related to:
Current year	(2,117)	(2,000)
Prior years	(518)	(543)
Total paid	(2,635)	(2,543)
Ending balance	541	591
Total IBNR	477
Individual Commercial
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	454	740
Less: Premium deficiency reserve	0	(176)
Balance	454	564
Incurred related to:
Current year	304	1,816
Prior years	(26)	(97)
Total incurred	278	1,719
Paid related to:
Current year	(223)	(1,396)
Prior years	(378)	(417)
Total paid	(601)	(1,813)
Premium deficiency reserve	0	(337)
Ending balance	131	$ 807
Total IBNR	$ 119